Swingarm concentric motor drive for electric motorcycle

ABSTRACT

A motorcycle includes an electric motor having an output shaft defining a motor axis, a rear wheel drivably coupled to the electric motor to propel the motorcycle, a swingarm rotatably supporting the rear wheel, and a frame. The frame includes a main frame member supporting the electric motor and the swingarm. A case of the electric motor is a stressed member of the frame between the main frame member and the swingarm. The swingarm is coupled to the case of the electric motor to define a swingarm pivot axis that is co-axial with the motor axis.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application No. 62/789,302, filed on Jan. 7, 2019, the entire contents of which are incorporated by reference herein.

BACKGROUND

The present invention relates to vehicles, and more particularly relates to motorcycles having a swingarm rear suspension and an electric drive motor

SUMMARY

In one aspect, the invention provides a motorcycle including an electric motor having an output shaft defining a motor axis, a rear wheel drivably coupled to the electric motor to propel the motorcycle, a swingarm rotatably supporting the rear wheel, and a frame. The frame includes a main frame member supporting the electric motor and the swingarm. A case of the electric motor is a stressed member of the frame between the main frame member and the swingarm. The swingarm is coupled to the case of the electric motor to define a swingarm pivot axis that is co-axial with the motor axis.

In another aspect, the invention provides a motorcycle including an electric motor operable to propel the motorcycle, wherein a case of the electric motor enclosing a rotor thereof is a stressed frame member of the motorcycle. A drivetrain of the motorcycle includes a drive sprocket rotatable by the electric motor, a driven sprocket coupled to a rear wheel of the motorcycle, and an endless drive member extended between the drive sprocket and the driven sprocket. A swingarm supports the rear wheel, and a pivot axis of the swingarm on the motorcycle is also the axis of rotation of both the drive sprocket and the rotor of the electric motor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a motorcycle according to one embodiment.

FIG. 2 is a right side view of the motorcycle of FIG. 1.

FIG. 3 is a left side view of the motorcycle of FIG. 1.

FIG. 4 is a perspective view of a portion of the motorcycle of FIG. 1, including a motor, a frame, and a swingarm.

FIG. 5 is an exploded assembly view of the portion of the motorcycle shown in FIG. 4.

FIG. 6 is a cross-section of the motorcycle, taken along line 6-6 of FIG. 3.

FIG. 7 is a detail view of an output side of the motor, taken from the cross-section of FIG. 6.

DETAILED DESCRIPTION

Before any aspects of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.

FIG. 1 illustrates a motorcycle 20 according to one embodiment of the present disclosure. The motorcycle 20 includes front and rear wheels 22, 24 (e.g., a single front wheel 22 and a single rear wheel 24 aligned with the front wheel 22 to define a single track). The motorcycle 20 includes a frame structure having a main frame 28. A front fork 32 supports the front wheel 22 ahead of the main frame 28. The front fork 32 is rotatably coupled to a head tube 36 of the main frame 28. Handlebars 40 are coupled to the front fork 32 to allow a rider to control the orientation of the front fork 32 and the front wheel 22. A rear swingarm 44 supports the rear wheel 24 for rotation therein, the rear swingarm 44 enabling pivoting suspension movements of the rear wheel 24 and the swingarm 44 together relative to the main frame 28 about an axis A (FIG. 4). In addition to the pivoting support at the axis A, the swingarm 44 is coupled to the main frame 28 through a shock absorber unit 46 (e.g., including a coil spring and a hydraulic damper). The motorcycle 20 further includes at least one seat 48 (e.g., saddle seat(s) for operator and optionally pillion passenger) and at least one set of foot supports 50 (e.g., laterally extending foot pegs).

As illustrated, the motorcycle 20 is an electric motorcycle operable to drive by an electric powertrain including an electric power store 54 (e.g., battery pack) and an electric motor 58 electrically coupled to the power store 54 to convert stored electrical energy from the power store 54 into rotational kinetic energy for driving the motorcycle 20. As illustrated, the motor 58 powers the rear wheel 24 through an endless drive member 62 (e.g., belt or chain) in the form of a loop wrapped around a drive sprocket 66 (FIG. 4) and a driven sprocket 68 that is fixedly secured to the rear wheel 24. As discussed in further detail below, the drive sprocket 66 that drives the endless drive member 62 is positioned to rotate about the axis A. Further, the drive sprocket 66 is fixed to rotate integrally with an output shaft 70 of the electric motor 58 about the axis A. As such, the motorcycle 20 is provided without a multi-speed transmission between the electric motor 58 and the drive sprocket 66, and without any gearbox whatsoever. This may further be facilitated by providing the electric motor 58 as a high pole count motor having high torque density.

With particular reference to FIGS. 4 and 5, the electric motor 58 forms an integral stressed member of the motorcycle frame, which includes as the primary member the main frame 28. The main frame 28 includes a backbone 28A extending rearward and downward from the head tube 36 and a front down tube 28B extending rearward and downward from the head tube 36 below the backbone 28A. Both the backbone 28A and the front down tube 28B are coupled rigidly to the electric motor 58 (e.g., at an outer periphery thereof). The portions of the backbone 28A and the front down tube 28B connecting to the electric motor 58 are separate and spaced from each other to separately couple to the electric motor 58. The backbone 28A is directly coupled to the electric motor 58 (e.g., with multiple fastener joints at a top of the motor), and the front down tube 28B is coupled indirectly to the electric motor 58 (e.g., with an intermediate bracket 74 and a plurality of fasteners at a position on the motor that is forward of the coupling of the backbone 28A). For the coupling of the main frame 28, the electric motor 58 can be provided with a plurality of bosses 76 as shown in FIG. 5 (e.g., bosses formed at the radially outer edge of the motor and adapted to receive fasteners extending parallel with the axis A). However, one or more alternate couplings can be used in addition to or in lieu of the illustrated bosses 76. The portion of the intermediate bracket 74 coupled to the electric motor 58 is forked into spaced-apart left and right parts. Similarly, the bottom ends of both the back bone 28A and the front down tube 28B are also forked. It is also noted that, for example at a bottom portion thereof, the electric motor 58 provides one or more mounting locations for the foot supports 50 such that the foot supports 50 depend from the electric motor 58 rather than another part of the frame such as the main frame 28. As illustrated, the foot supports 50 include left and right foot pegs coupled to each other and to the electric motor 58 by a central foot support bracket 78 extending between the foot supports 50.

Turning now to the swingarm 44, and referring particularly to FIGS. 5 to 7, two pivoting joints between the swingarm 44 and the electric motor 58 are formed with respective cylindrical bosses 82 of a motor housing or case 84 provided to contain the motor's rotor 86. The rotor 86 is a rotating assembly, for example including permanent magnets, that is driven to rotate relative to a stator (not shown) and the motor case 84 when the motor 58 is energized. The case 84 can be formed in multiple pieces that join together for assembly, for example parallel to the axis A. In some constructions, the motor case 84 may fully or partially contain power electronics for communicating electric power from the power store 54 to the electric motor 58. The bosses 82 are formed to protrude axially beyond axial end faces (e.g., flat or flat, ribbed plates) of the case 84. As such, the bosses 82 may form the widest point of the case 84. As shown in FIGS. 6 and 7, the boss 82 on the drive side (rider's right as shown) may be formed as an insert separate from the portion of the case 84 that extends radially outward from the axis A to cover the rotor 86, although other constructions are optional. The output shaft 70 exits through the boss 82 on the drive side. On the non-drive side, the illustrated boss 82 is integrally formed with a portion of the case 84 that extends radially to the outer periphery of the case 84, and may also extend in a widthwise, axial direction over part or all of the rotor 86. At each swingarm joint, a front forked end portion 90 of the swingarm 44 is joined with the respective boss 82 (e.g., through a bearing 92 such as a roller bearing). Swingarm bearing clamps 94 are fastened to the front forked ends 90, around outer races of the bearings 92, to retain the swingarm 44 in position relative to the axis A. Each swingarm bearing clamp 94 includes features, such as a channel flanked by end flanges or shoulders, that position the swingarm 44 to the motor 58 as shown in FIG. 7. By the arrangement shown and described herein, the swingarm 44 is pivotably supported on the motor case 84 about the axis A, which is the axis of the rotor 86 and the output shaft 70 of the motor 58, along with the drive sprocket 66. Loads from the rear wheel 24 to the swingarm 44 are further transmitted to the main frame 28 only indirectly. In particular, loads at the swingarm 44 are transmitted through two possible paths: through the shock absorber unit 46 to a shock absorber mount 28C of the main frame 28, and through the motor case 84 to the main frame 28.

The swingarm joint on the drive side, along with the drive sprocket 66, is concealed partially or wholly by a cover 96 (FIGS. 1 and 2) secured to the motor case 84, although the cover 96 is removed for clarity in FIGS. 4-7. An additional enclosure 100 (FIGS. 1-3) directly forward of the electric motor 58 contains power electronics for providing the driving electric power signals to the motor 58. For example, one or any combination of: the motor inverter, the charger, and the DC/DC converter may be provided within the enclosure 100. The power electronics enclosure 100 can be provided by one or more individual pieces coupled to the motor 58, thus forming a motor assembly or power unit with integrated electronics.

As shown in FIG. 6, the rotor 86 within the motor 58 has a cross-sectional shape that is significantly wider in the axial direction at its outer radial ends, furthest from the axis A as compared with its inner radial portion. For example, the rotor 86 may have the cross-sectional shape of an “I” when sectioned along the axis A (i.e., a cross-section, as FIG. 6, taken along a plane that contains the axis A). The axially-measured rotor width W is a function of radius that increases by a factor of 4, 5 or more in the radial direction from the inner portion of the rotor 86 that is secured to the output shaft 70 to a widest point adjacent the radial outer end. As shown in FIG. 6, this shape creates large voids or pockets whereby first and/or second bearings 104, 106 can be at least partially nested into the rotor 86 (and in some cases fully nested therein). The first bearing 104 is provided on a side of the rotor 86 opposite the drive side. The second bearing 106 is provided on the drive side of the rotor 86, adjacent the drive sprocket 66. The second bearing 106 can have a larger load rating than the first bearing 104. The second bearing 106 can have a greater width than the first bearing 104 and/or a greater number of rows of rolling elements therein (e.g., single row vs. multi-row). The first and second bearings 104, 106 are the only bearings supporting the output shaft 70 relative to the case 84 and are positioned entirely within an exterior width profile of the case 84, even when measured to exclude the projection of the bosses 82. In some constructions, as shown, the axial end faces of the case 84 are flat radially outward of the bosses 82, and the first and second bearings 104, 106 are entirely between these two flat axial end faces. As shown in FIG. 6, a sensor 108 (e.g., rotational position sensor) for the motor 58 is positioned within the boss 82 on the non-drive side.

In the axial direction, the part of the swingarm 44 that is on the drive side is positioned between the adjacent axial end face of the motor case 84 and the drive sprocket 66. In other words, the drive sprocket 66 is positioned outboard of the swingarm pivot joint. A spacer ring 112 may be provided axially between the drive sprocket 66 and the swingarm pivot joint, and this may be the only component positioned axially therebetween. The spacer ring 112 can abut a shoulder on the output shaft 70 to set the correct position of the drive sprocket 66 for alignment with the driven sprocket 68 on the rear wheel 24. A bolt 116 threaded into the output shaft 70 secures the drive sprocket 66 to an axial end of the output shaft 70, with or without a separate washer. The drive sprocket 66 is splined, keyed or otherwise locked for integral rotation with the output shaft 70.

The above-described construction provides for an electric motorcycle motor 58 having an output axis A that is co-axial with the swingarm pivot axis. Furthermore, there is no separate pivot shaft for the swingarm 44 whatsoever, as the forward ends of the swingarm 44 interface with supporting portions (e.g., bosses 82) of the motor case 84, with only bearings 92 therebetween. Pivoting the swingarm 44 co-axially with the motor output axis A enables the motorcycle 20 to accommodate a wide range of suspension travel as it eliminates variation in center distance between the drive sprocket 66 and the driven sprocket 68 throughout the travel of the swingarm 44. Tension in the endless drive member 62 does not vary with suspension travel, and this improves durability while allowing the tension to be optimized for efficiency.

Various features and advantages of the invention are set forth in the following claims. 

What is claimed is:
 1. A motorcycle comprising: an electric motor having an output shaft defining a motor axis; a rear wheel drivably coupled to the electric motor to propel the motorcycle; a swingarm rotatably supporting the rear wheel; and a frame including a main frame member supporting the electric motor and the swingarm, wherein a case of the electric motor is a stressed member of the frame between the main frame member and the swingarm, wherein the swingarm is coupled to the case of the electric motor to define a swingarm pivot axis that is co-axial with the motor axis.
 2. The motorcycle of claim 1, wherein an end of the output shaft exits the motor case and supports in fixed relation thereon a drive sprocket coupled to a driven sprocket of the rear wheel by an endless drive member.
 3. The motorcycle of claim 1, wherein the main frame member includes a backbone and a front down tube, the two of which are independently secured to an outer periphery of the case of the electric motor.
 4. The motorcycle of claim 1, wherein a drive sprocket for driving the rear wheel through an endless drive member is situated along the motor axis at a position outboard of the swingarm.
 5. The motorcycle of claim 1, wherein a forward end of the swingarm includes left and right sides joined to the electric motor case with respective bearings to form respective swingarm pivots on the motor axis.
 6. The motorcycle of claim 5, wherein the respective bearings are enclosed by respective bearing clamps fastened to the forward end of the swingarm.
 7. The motorcycle of claim 1, wherein a rotor of the electric motor has a cross-sectional shape of an “I” forming respective pockets on respective ends thereof, the motorcycle further comprising first and second bearings supporting the rotor in the case of the electric motor, wherein the first and second bearings are nested within the respective pockets of the rotor.
 8. The motorcycle of claim 7, wherein the first bearing is remote from a drive side having a drive sprocket and the second bearing is adjacent the drive side, the second bearing having a dimension along the pivot axis that is larger than a similarly-measured dimension of the first bearing.
 9. The motorcycle of claim 1, further comprising a set of foot supports depending from the electric motor case.
 10. A motorcycle comprising: an electric motor operable to propel the motorcycle, wherein a case of the electric motor enclosing a rotor thereof is a stressed frame member of the motorcycle; a drivetrain including a drive sprocket rotatable by the electric motor, a driven sprocket coupled to a rear wheel of the motorcycle, and an endless drive member extended between the drive sprocket and the driven sprocket; a swingarm supporting the rear wheel, wherein a pivot axis of the swingarm on the motorcycle is also the axis of rotation of both the drive sprocket and the rotor of the electric motor.
 11. The motorcycle of claim 10, wherein the drive sprocket is mounted on an output shaft of the electric motor.
 12. The motorcycle of claim 10, wherein the drive sprocket is situated along the pivot axis at a position outboard of the swingarm.
 13. The motorcycle of claim 10, wherein a forward end of the swingarm includes left and right sides joined to the electric motor case with respective bearings to form respective swingarm pivots on the pivot axis.
 14. The motorcycle of claim 13, wherein the respective bearings are enclosed by respective bearing clamps fastened to the forward end of the swingarm.
 15. The motorcycle of claim 10, wherein the rotor has a cross-sectional shape of an “I” forming respective pockets on respective ends thereof, the motorcycle further comprising first and second bearings supporting the rotor in the case of the electric motor, wherein the first and second bearings are nested within the respective pockets of the rotor.
 16. The motorcycle of claim 15, wherein the first bearing is remote from the drive sprocket and the second bearing is adjacent the drive sprocket, the second bearing having a dimension along the pivot axis that is larger than a similarly-measured dimension of the first bearing.
 17. The motorcycle of claim 10, further comprising a set of foot supports depending from the electric motor case. 